Back to the future! The accuracy can be as good, but you have to have accurate art work to start with so your theory of not spending much time programming is false. The amount of time I spend "programming" after generating the drawing (which you have to do with either method) is in minutes. The line followers are 70's technology and I have converted several to CNC. Once you understand that you don't have to "program" anything the CNC approach makes a lot more sense.
Do some research on the modern way to cut with plasma. I can do in seconds what it will take you hours to setup and do. Since all of my cuts are different then it means new artwork for each part.
see:
www.sheetcam.com www.artofcnc.ca
The steps are easy to define:
Draw the part in CAD or a Drawing Package. This step would probably be the same unless you intend to sit down and draw shapes on large pieces of paper (then accuracy is only as good as you can draw and measure by hand). Then you use a low cost CAM program (
www.sheetcam.com) to define HOW you want the cut (inside, outside offsets, lead-ins, pierce cycles, etc) all things you will have to do manually on an optical table. Takes maybe 5 minutes on simple parts and 10 on very complex ones and you hit a button and 1 sec later you have hundreds (even thousands) of lines of g-code with all of the right moves. It optimizes the cuts, figures the correct start points and pierce cycles and puts them in a file that runs on your table controller.
The biggest time investment you will have to make is going to be in learning the drawing part, and to get accuracy computers will run circles around a person drawing on paper. The rest of the equation is a lot simplier.
A lot of builders get intimidated by the electronics part of the build. CNC is complex and there are a lot of things to get your head around expecially if you are building it from scratch, but there are more and more turn-key solutions are attractive price points.
Read, study and try to learn as much as you can about modern low cost CNC for plasma. If you still want to buy an optical tracer table then just be aware that if it breaks (especially the electronics) you will have to find someone that can still work on old electronics and pay the fees. replacement parts are often impossible to find so you have to re-engineer a section and if you don't have the full documentation on the table you need a physic along for help!
We have non-technical guys building plasma tables on this list. You don't have to be an electronics wizard or a machinist to build a table. You can even buy tables in various stages of completion. Check the guys at EZ-Router (
www.EZ-Router.com) they have sold gantry systems and combo electronic/gantry/drive systems to builders that wanted to concentrate on the table mechanicals.
Tom Caudle
www.CandCNC.com 
11-22-2006, 05:00 AM
Linear Mode
